1. Field of Invention
This invention relates generally to short-circuit or faulted circuit indicator (FCI) apparatuses for use in electrical power distribution systems. More particularly, it relates to a faulted circuit indicator device which has an improved clamping mechanism of a unique physical construction so as to reduce mechanical stress on an electrical cable during mounting and removal of the faulted circuit indicator device and to automatically secure the cable in a central position.
2. Description of the Prior Art
As is generally known in the art, there exist a number of faulted circuit indicator devices for use in electrical power distribution systems to monitor circuit conditions in order to detect and determine the location of malfunctions occurring in the system. In particular, such prior art faulted circuit indicator devices are of the clamp-on type which typically includes a housing having fault monitor circuitry responsive to an abnormally high electric current, an indicator unit, and a clamping mechanism for mounting the housing onto overhead power lines, electrical conductor cables, bus bars, and the like. In addition, the faulted circuit indicator devices are generally installed or mounted about the energized conductor cable to be monitored by the use of a conventional shot-gun stick. The shot-gun stick is sometimes referred to as a “hot-stick” which is utilized to separate a spring-biased clamping mechanism for mounting the faulted circuit indicator device over and onto the energized conductor cable.
One such prior art faulted circuit indicator device of the clamp-on type is described and illustrated in U.S. Patent Application Publication No. 2009/0009274 to H. Horstmann published on Jan. 8, 2009 and assigned to the same assignee as the present invention. This Publication No. 2009/0009274 shows a short-circuit indicator for arrangement on an electrical line for electrical power distribution which includes a current transformer. The current transformer has an induction coil and an iron yoke for surrounding the electrical line to be monitored for a short-circuit current. The induction coil is seated on a base web of a U-shaped first yoke part. A second yoke part is connected in the form of a joint which can move between a closed position and an open position to one of two U-limbs of the first yoke part. The second yoke part forms a magnetic return path element for the first yoke part in the closed position. The first yoke part is split into two-essentially L-shaped parts in the area of the base web to which the induction coil is fitted.
Further, there is illustrated in FIG. 8 of the drawings and labeled as “Prior Art” a faulted circuit indicator device 110 of the clamp-on type made by and also assigned to the assignee of the instant invention, which is mounted about an overhead cable or conductor 112 in which the current passing therethrough is to be monitored. As can be seen, the faulted circuit indicator device 110 is comprised of essentially rectangular-shaped housing 114, a pair of C-shaped clamp arms 116 (only one is shown), a spring-biased clamp arm 118, a wire/spring bail 120, and an indicator unit 122. The cable 112 is sandwiched between the C-shaped clamp arms 116 and the spring-biased clamp arm 118. The wire bail 120 extends from the lower end of the housing 114 and is pullable by the conventional shot-gun stick for installation onto the cable.
One of the disadvantages of the prior art device of FIG. 8 is that a substantial amount of mechanical stress is created on the cable by the spring-biased clamp arm 118 during mounting and removal of the faulted circuit indicator device 110. In particular, when mounting the faulted circuit indicator device mechanical stress is created since the cable 112 must be pushed upwardly with a strong force against the spring-biased clamp arm 118. Similarly, when removing the faulted circuit indicator device mechanical stress is created since the cable 112 must be pulled downwardly with a strong force against the spring-biased clamp arm 118. Another disadvantage is that the cable 112 is not always secured horizontally in the C-shaped clamp arms 116 in a central position during installation.
It would be desirable to provide a faulted circuit indicator device which is designed with an improved clamping mechanism so as to relieve or reduce mechanical stress on the cable during its installation or removal. Further, it would be expedient that the clamping mechanism of the faulted circuit indicator secures automatically the cable horizontally in a central position.
The present invention represents a significant improvement over the aforementioned Publication No. 2009/0009274 and the prior art device of FIG. 8. The faulted circuit indicator device of the present invention includes an improved clamping mechanism formed of a yoke and a pair of opposed pressure plates for automatically holding horizontally a cable therebetween in a fixed central position.